Solvent transference numbers and solvation energies of silver sulphate in mixtures of methanol and n-methylformamide

The solvent transference number, Δ, of Ag2SO4 in mixtures of methanol and Nmethylformamide (NMF) was determined by e.m.f. experiments using a galvanic cell with transference as introduced by C. Wagner [4]. The solvent composition was varied over the entiremole fraction range, corresponding to a change in the dielectric constant from 32 to 180 by abouta factor of 6. The solvent transference number was always not equal zero which means that thereis a preferred transport of NMF towards the cathode compartment. passes through two maximal values with changing mole fraction and decreases to nearly zero in the mixture; thisbehaviour is unusual when compared with results from otherpolar solvent mixtures. With the help of the Gibbs energies of solvation of the ionic species obtained from additionalexperimentsit could be shown that the special behaviour of is due to a transition from heteroselective solvation to homoselective solvation of Ag2SO4 by NMF. © by Akademische Verlagsgesellschaft